I seem to remember this movie starts with kids running around playing when a certain boy & girl are singled out. Some how lead to know that they are in love boyfriend/girlfriend. Then a man/angel comes in & calls the boy to let him know it is his turn to be born to parents on earth. So we figure out they are in love & in Heaven waiting to be born. The boy doesn't want to go without the girls then I seem to remember the angel tells the boy she will be born six years later & that if it is Gods will or true love they will find each other again later in life on earth.

The Blue Bird (1940)
starring Shirley Temple (RIP)
IMDb synopsis:
Mytyl and her brother Tyltyl, a woodchopper's children, are led by the Fairy Berylune on a magical trip through the past, present, and future to locate the Blue Bird of Happiness.
The Blue Bird (1940) - IMDb

It also might be in the 1976 remake.

Here's the scene from the 1940 film:
The Blue Bird 1940 part 8 of 10 - YouTube


EDIT: There's another movie in which people fall in love in Heaven then come to Earth, but they're portrayed by adult actors: Made in Heaven (1987) http://www.imdb.com/title/tt0093467/